Burnishing tool



Dec. 8, 1936. w. r. PRITCHARD ET AL 2,063,338

BURNI SHING TOOL Filed April 1, 1936 n4 r. PR/TCHA R0 MFA/TOPS A RSAUNDERS A T TORNE V Patented Dec. 8, 1936 UNITED STATES PATENT QIFFIfiEBURNISHING TOOL Application April 1, 1936, Serial No. 72,064

3 Claims.

This invention relates to a burnishing or cleaning tool and moreparticularly to a tool for cleaning and burnishing the contact surfacesof the terminals of selector banks.

Selector switches of the well known panel type, such for example asdisclosed in Patent 1,123,695 granted January 5, 1915 to E. B. Craft andJ. N. Reynolds, are installed in groups side by side on mounting frames.Each switch shaft is equipped with a plurality of sets of brushes andthe brush sets of all switches on the same frame have common access to aflat bank of multipled terminals. The terminal bank is divided into asmany horizontal sections as there are brush sets on each switch so thateach horizontal bank section is allocated to the corresponding brushsets of the selector switches. Each bank section is provided with aplurality of vertical rows of sets of terminals with which a set ofnormally inactive switch brushes cooperam. These rows of terminals aremultipled horizontally across the bank to be accessible to all of theswitches on the frame. When a switch is operated a set of brushes istripped for cooperation with the vertical rows of terminals of a banksection and the brushes are then advanced to successively engage theedges of the contacts to establish circuits thereover.

Considering the switch and bank structures as briefly described above,it will be apparent that it is essential to maintain the surfaces of theterminals with which the switch brushes engage in a bright, cleancondition in order that there may be good electrical conduction betweenthe brushes and contacts. It is therefore the object of the presentinvention to provide a tool by means of which the contact surfaces ofthe vertical rows of terminals may be burnished to remove dust orcorrosion which would otherwise increase the contact resistance betweensuch terminals and brushes and reduce the electrical efficiency of thecircuits established thereover.

In accordance with the present invention the tool comprises a split armhaving a pistol grip handle on one end and insulating blocks attached tothe two sections of the arm at the other end, a heavy rubber bandsurrounding the blocks, a screw for spreading the two sections of thearm for varying the thickness of the rubber band, and a steel springattached to the upper edge of the arm near the handle, in the bifurcatedend of which may be secured the ends of a strip of abrasive cloth whichmay be passed around the rubber band and held taut by the spring. Inusing the tool the end thereof upon which the abrasive cloth is securedis inserted between two vertical rows of terminals of the contact bankand moved slowly up or down the entire height of the bank.

For a clearer understanding of the invention reference may be had to thefollowing detailed description taken in connection with the accompanyingdrawing in which: I

Fig. 1 is a side perspective View of the tool equipped with a strip ofabrasive cloth in readiness for use;

Fig. 2 shows the end of the tool, partly in crosssection, with therubber band and strip of abrasive cloth disassembled therefrom; and

Fig. 3 shows a portion of the face of a termi- 15 nal bank and themanner in which the tool is applied for burnishing the terminals.

The tool comprises an arm I having a pistol grip handle 2 attached toone end thereof by the rivets 3. The arm is slit from a point adjacentthe handle to the other end to form two sections 4 and 5, section 5being narrow enough to permit it to be flexed. The ends of the sectionsare provided with slotted enlargements 6 and I within which narrowblocks 8 and 9 of insulating material are secured by the screws I0. Theblocks of insulating material are provided for the purpose of preventingcross-connection between adjacent terminals of the bank when the tool isin use.

Surrounding the blocks 8 and 9 is a heavy band I I of rubber, thethickness of which may be varied by the spreading of the outer end ofthe two sections of the arm I by the adjustment of the screw I2. ScrewI2 is threaded into the enlarged por- 35 tion I of the lower section 5of arm I and its end engages in a recess in the enlarged portion 6 ofthe upper section 4 of the arm. When the screw is turned the lowersection 5 of the arm is flexed and the insulating block 9 is therebyseparated from the block 8, stretching the rubber band I I.

Secured by screws I3 to the upper edge of the arm I near the pistol gripis a steel spring I4. The free end of this spring extends to a pointover the band II and is slotted as shown at I5 to receive the ends of astrip of abrasive cloth.

To prepare the tool for use the band II is slipped over the blocks 8 and9 and a strip I6 of abrasive cloth or other suitable abrasive mate-'rial is wrapped around the band II. The spring I 4 is then depressed andthe ends of the strip I6 are engaged in the slot I5 of the spring. Whenpressure on the spring is now released the spring draws the strip I6taut around the band. The

tool may now be applied to the terminal bank with its end positionedbeneath the space between two adjacent vertical rows of terminals andthen moved up or down between the rows of terminals. This movement ofthe tool draws the abrasive strip across the contacting edges of theterminals as disclosed in Fig. 3 thereby removing particles of dust,corrosion or roughness therefrom.

To adjust the tool for varying spacing between rows of terminals thescrew I2 is turned as previously described to spread the blocks 8 and 9and thereby stretch the band I I. The stretching of the band willobviously result in reducing the thickness of its side walls andconsequently the thickness of the abrasive end of the tool.

What is claimed is:

1. In'a burnishing or cleaning tool, an arm having a handle connected toone end thereof and having the other end thereof slit longitudinally, anelastic band surrounding the slit end of said arm, adjustable means forexpanding the slit end of said arm for varying the thickness of saidelastic band, a strip of abrasive material surrounding said band andmeans for holding said strip of abrasive material upon said band.

2. In a burnishing or cleaning tool, an arm having a handle connected toone end thereof and having the other end thereof slit longitudinally, anelastic band surrounding the slit end of said arm, adjustable means forexpanding the slit end of said arm for varying the thickness of saidelastic band, a strip of abrasive material surrounding said band and aspring member secured to said. arm and having a bifurcated free endwithin which the free ends of said strip are secured and by which saidstrip is held taut on said band.

3. In a burnishing or cleaning tool, an arm having a handle connected toone end thereof and having the other end thereof slit longitudinally,insulating blocks secured in the ends of the two sections of the slitend of said arm, an elastic band surrounding said insulating block, anadjusting screw for expanding the slit end of said arm for varying thethickness of said elastic band, a strip of abrasive material surroundingsaid band and means for holding said strip of abrasive material uponsaid band.

' WILLIAM T. PRITCHARD.

ARTHUR R. SAUNDERS.

